The Mysterious Barium Stars Robert Izzard Tyl Dermine Argelander Institute for Astronomy, Institute of Astronomy and Astrophysics, University of Bonn Universite Libre de Bruxelles Robert Izzard (AIfA, Bonn) The Mysterious Barium Stars - NAM 2011 - Llandudno, Wales 1 What is a barium star? 100% binaries! Complete observation set of periods and eccentricities Robert Izzard (AIfA, Bonn) The Mysterious Barium Stars - NAM 2011 - Llandudno, Wales 2 How to make a Ba star? A long time ago... Robert Izzard (AIfA, Bonn) The Mysterious Barium Stars - NAM 2011 - Llandudno, Wales 3 How to make a Ba star? A long time ago... Robert Izzard (AIfA, Bonn) The Mysterious Barium Stars - NAM 2011 - Llandudno, Wales 4 How to make a Ba star? A long time ago... Post-AGB → PN Robert Izzard (AIfA, Bonn) The Mysterious Barium Stars - NAM 2011 - Llandudno, Wales 5 How to make a Ba star? A long time ago... Robert Izzard (AIfA, Bonn) The Mysterious Barium Stars - NAM 2011 - Llandudno, Wales 6 The barium star now Robert Izzard (AIfA, Bonn) The Mysterious Barium Stars - NAM 2011 - Llandudno, Wales 7 Tidal Circulari[sz]ation τ ∼ (a/R)8 Robert Izzard (AIfA, Bonn) The Mysterious Barium Stars - NAM 2011 - Llandudno, Wales 8 Observations: GK giants (Jorissen data) Period / days 100 1000 10000 0.9 0.8 0.7 0.6 0.5 0.4 Eccentricity 0.3 0.2 0.1 0 Robert Izzard (AIfA, Bonn) The Mysterious Barium Stars - NAM 2011 - Llandudno, Wales 9 Expected result for Ba stars Period / days 100 1000 10000 0.9 0.8 Circularization! 0.7 0.6 0.5 0.4 Eccentricity 0.3 0.2 0.1 0 Robert Izzard (AIfA, Bonn) The Mysterious Barium Stars - NAM 2011 - Llandudno, Wales 10 Observations say otherwise! Period / days 100 1000 10000 1 0.9 0.8 0.7 0.6 0.5 0.4 Eccentricity 0.3 0.2 0.1 0 Robert Izzard (AIfA, Bonn) The Mysterious Barium Stars - NAM 2011 - Llandudno, Wales 11 Thesis: Natal kick for the white dwarf Young WD Single and binary stars! Old WD/MS Fregeau et al ApJ 695, 20 Heyl MNRAS 381,385 etc. Davis et al MNRAS 383, 20 Robert Izzard (AIfA, Bonn) The Mysterious Barium Stars - NAM 2011 - Llandudno, Wales 12 Curry Kick Scale What is the effect on the Barium Stars? Curry Kick Velocity/km s−1 English 0 Korma 1 Dopiaza 2 Dhansak 3 Madras 4 Vindaloo 7 Phall 100 Robert Izzard (AIfA, Bonn) The Mysterious Barium Stars - NAM 2011 - Llandudno, Wales 13 Canonical result (no kick) Observations: Jorissen et al (1998) 1 0.8 0.6 0.4 Eccentricity 0.2 0 2 3 4 5 log10(Period/days) Robert Izzard (AIfA, Bonn) The Mysterious Barium Stars - NAM 2011 - Llandudno, Wales 14 Korma kick 1 kms−1 1 0.8 0.6 0.4 Eccentricity 0.2 0 2 3 4 5 log10(Period/days) Robert Izzard (AIfA, Bonn) The Mysterious Barium Stars - NAM 2011 - Llandudno, Wales 15 Dopiaza kick 2 kms−1 1 0.8 0.6 0.4 Eccentricity 0.2 0 2 3 4 5 log10(Period/days) Robert Izzard (AIfA, Bonn) The Mysterious Barium Stars - NAM 2011 - Llandudno, Wales 16 Dhansak kick 3 kms−1 1 0.8 0.6 0.4 Eccentricity 0.2 0 2 3 4 5 log10(Period/days) Robert Izzard (AIfA, Bonn) The Mysterious Barium Stars - NAM 2011 - Llandudno, Wales 17 Madras kick 4 kms−1 1 0.8 0.6 0.4 Eccentricity 0.2 0 2 3 4 5 log10(Period/days) Robert Izzard (AIfA, Bonn) The Mysterious Barium Stars - NAM 2011 - Llandudno, Wales 18 Vindaloo kick 7 kms−1 1 0.8 0.6 0.4 Eccentricity 0.2 0 2 3 4 5 log10(Period/days) Robert Izzard (AIfA, Bonn) The Mysterious Barium Stars - NAM 2011 - Llandudno, Wales 19 Phall! 100 kms−1 1 0.8 0.6 0.4 Eccentricity 0.2 0 2 3 4 5 log10(Period/days) Robert Izzard (AIfA, Bonn) The Mysterious Barium Stars - NAM 2011 - Llandudno, Wales 20 Phall! 100 kms−1 1 0.8 0.6 0.4 Eccentricity 0.2 0 2 3 4 5 log10(Period/days) Robert Izzard (AIfA, Bonn) The Mysterious Barium Stars - NAM 2011 - Llandudno, Wales 21 −1 Madras please! (4 kms ) Still Problems! 1 0.8 Long-P tail 0.6 0.4 Eccentricity Period gap! 0.2 0 2 3 4 5 log10(Period/days) Robert Izzard (AIfA, Bonn) The Mysterious Barium Stars - NAM 2011 - Llandudno, Wales 22 4km/s kick+efficient CE ejection (bad curry?) 1 0.8 0.6 0.4 Eccentricity 0.2 0 2 3 4 5 log10(Period/days) Robert Izzard (AIfA, Bonn) The Mysterious Barium Stars - NAM 2011 - Llandudno, Wales 23 ˙ 4km/s kick + efficient CEE and Jorb 1 0.8 0.6 0.4 Eccentricity 0.2 0 2 3 4 5 log10(Period/days) Izzard, Dermine & Church (2010) A&A 523, 10 Robert Izzard (AIfA, Bonn) The Mysterious Barium Stars - NAM 2011 - Llandudno, Wales 24 Newsflash! Circumbinary Discs! Post-AGB = Ba progenitor 25% are binaries these all have CB Discs Tyl Dermine is modelling these Artymowicz & Lubow 1996 Deroo et al. 2007 Robert Izzard (AIfA, Bonn) The Mysterious Barium Stars - NAM 2011 - Llandudno, Wales 25 CB Disc Models for post-AGB stars 1 0.8 0.6 0.4 0.2 0 1 Eccentricity 0.8 0.6 0.4 0.2 0 100 101 102 103 104 105 Period/days Robert Izzard (AIfA, Bonn) The Mysterious Barium Stars - NAM 2011 - Llandudno, Wales 26 Conclusion: How To Make Barium Stars...? Efficient J loss e Ba starsKick? Efficient CE Disc? P Many thanks! Robert Izzard (AIfA, Bonn) The Mysterious Barium Stars - NAM 2011 - Llandudno, Wales 27 ......... Robert Izzard (AIfA, Bonn) The Mysterious Barium Stars - NAM 2011 - Llandudno, Wales 1 Globular Cluster models Robert Izzard (AIfA, Bonn) The Mysterious Barium Stars - NAM 2011 - Llandudno, Wales 2 Kick Implications: PNe (TT Cygni in CO) Robert Izzard (AIfA, Bonn) The Mysterious Barium Stars - NAM 2011 - Llandudno, Wales 3 Kick Implications: PNe (TT Cygni in CO v ∼ 0.6 km s−1) Robert Izzard (AIfA, Bonn) The Mysterious Barium Stars - NAM 2011 - Llandudno, Wales 4 Efficient common envelope ejection? ◮ As if we have a clue?! ◮ Envelope weakly bound ◮ Even with α = 1 only a few % of envelope’s recombination energy is required ◮ Nelemans/Tout γ prescription →similar! ◮ Only for P . 2000 days Robert Izzard (AIfA, Bonn) The Mysterious Barium Stars - NAM 2011 - Llandudno, Wales 5 Angular momentum? ◮ Huang 1956: ◮ when the lost mass is collected by the secondary component, the major axis will decrease ˙ ˙ M ˙ ◮ Jorb ∝ − M1 − 2 M2 M1 ◮ Second term large for efficient accretion! ˙ Jorbit ˙ ˙ ◮ Jorbit = l M1 + M2 M1+M2 (l & 2) ◮ Alternatively: ◮ magnetic braking ◮ disc mass loss? Robert Izzard (AIfA, Bonn) The Mysterious Barium Stars - NAM 2011 - Llandudno, Wales 6 Efficient accretion: Mira Robert Izzard (AIfA, Bonn) The Mysterious Barium Stars - NAM 2011 - Llandudno, Wales 7.